Now, am I 100% certain that James isn’t alluding to canonical Job when he talks about the “perseverance of Job”? Well, no. But I am pretty certain that something more than just canonical Job is in view. I am no expert in Jewish culture of the 1st century, but we do know that New Testament writers can be aware of and allude to the broader scope of Jewish literature available to them. There are some Biblical figures (Adam, Enoch, Noah, Abraham and Job for starters) who inspired additional literature outside of the Biblical books that we are familiar with, and these books clearly held some currency in the time of the New Testament. We also need to remember that this is a period with a low literacy rate, so when James says “you have heard of the perseverance of Job,” that’s precisely what he means–you guys have heard stories about Job’s patience. He may not be referring to a specific text as much as an oral tradition that strongly linked “patience” to Job as his most noted quality. But it’s hard to imagine that The Testament of Job hasn’t either originated or strongly reinforced that link, and if James has one specific written text in mind, I’m putting my money on Testament rather than canonical Job. The former make a huge point out of Job’s calm acceptance and perseverance; the latter simply doesn’t.
This analogy isn’t perfect, but readers of the New Testament need to remember that first century Judaism was a lot more like Catholicism than evangelical Protestantism. You have mystic groups, ascetics, extra-Biblical traditions and alternative texts all living alongside or in tension with the approved religious hierarchy. When a Catholic talks about Mary, they are tapping into a whole stream of images, references, doctrine and devotional literature that ultimately originates with the presentation of Mary in the gospels, but with so many accretions that most Protestants feel that they don’t recognize that Mary at all. Everyone understands that when a Southern Baptist sings “Mary Did You Know?” and a Roman Catholic sings “Ave Maria” there’s a sense in which they are addressing the same person, but in many ways they really aren’t.
And when James says “you’ve heard of the perseverance of Job,” he probably isn’t excluding canonical Job from that reference (again, you can find support for the patience tradition in the prose framework) but he’s almost certainly including much more as well.
You can see the same thing in 2 Peter 2:4-9:
4 For if God did not spare angels when they sinned, but sent them to hell, putting them into gloomy dungeons to be held for judgment; 5 if he did not spare the ancient world when he brought the flood on its ungodly people, but protected Noah, a preacher of righteousness, and seven others; 6 if he condemned the cities of Sodom and Gomorrah by burning them to ashes, and made them an example of what is going to happen to the ungodly; 7 and if he rescued Lot, a righteous man, who was distressed by the filthy lives of lawless men 8 (for that righteous man, living among them day after day, was tormented in his righteous soul by the lawless deeds he saw and heard)— 9 if this is so, then the Lord knows how to rescue godly men from trials and to hold the unrighteous for the day of judgment, while continuing their punishment.
Scholars have noted many similarities between 2 Peter and Jude, not least of which is that they both allude to 1 Enoch–that’s where this weird bit about angels in gloomy dungeons comes from. Similarly, there is nothing in Genesis about Noah preaching, but it was well-known in Jewish tradition, especially in the Sibylline Oracles, which record one of Noah’s sermons in 1:148-198. And when I read Genesis, canonical Lot doesn’t come across as particularly righteous (getting drunk and impregnating his own daughters falls somewhat short of praise-worthiness), but the Lot of Jewish tradition was one of the good guys:
Jewish tradition interpreted Abraham’s plea on behalf of the righteous in Sodom (Gen 18:23–32) as referring to Lot (Pirqe R. El. 25; Gen. Rab. 49:13), and so could speak of him as a righteous man (Wis 10:6; 19:17: δίκαιος; cf. 1 Clem 11:1: Philo, Mos. 2.58). His exemplary deliverance from the fate that overtook his wicked fellow-citizens is mentioned in Wis 10:6; Philo, Mos. 2.58; and 1 Clem 11:1, which seem to belong to the same paraenetic tradition as 2 Pet 2:4–9.
-Richard J. Bauckham, vol. 50, Word Biblical Commentary : 2 Peter, Jude, Word Biblical Commentary (Dallas: Word, Incorporated, 2002), 252.
It is beyond reasonable dispute that the New Testament epistles include non-canonical information about Moses, Noah, Lot, and angels. Does it seem like a stretch to think the same thing is at play with Job? Not to me.
So it’s a bit simplistic to say “James mentions Job, therefore Job must be historical.” First of all, even if there were no extrabiblical Job traditions, a New Testament reference is no proof of historicity. Suppose James had written “you have heard of the compassion of the Good Samaritan”? That’s completely intelligible and serves as the basis for moral exhortation, but without requiring that the Samaritan was a historical person. All that is required is that there is a known religious tradition that includes a Samaritan story, and that the tradition was accepted as relevant for moral instruction. James isn’t citing Job because he necessarily thinks Job is historical. He may not have even thought about it one way or the other. The “patience of Job” tradition is a shared cultural inheritance he and his audience both know, and it is relevant for the instruction he is giving. That’s about all that citation proves: shared knowledge and relevance. If someone really wants to posit that a New Testament allusion necessarily implies historicity, then I guess you get your trump card for claiming strict historicity for canonical Job and Jonah, but you are also going to get, at bare minimum, 1 Enoch, the Assumption of Moses, and the Sybilline Oracles in the process. If citation proves historicity, things get really interesting in a hurry.